1. Field of the Invention
The present invention relates to an apparatus for joining the ends of belt-shaped members, such as rubberized cord layers constituting a pneumatic tire.
2. Description of the Related Art
As a conventional apparatus for joining the ends of belt-shaped members, one disclosed in, for instance, U.S. Pat. No. 4,765,862 is known. The apparatus in the justmentioned invention comprises: a first conveyor extending in the longitudinal direction of the belt-shaped member; a second conveyor disposed in a direction of the first conveyor and extending in the longitudinal direction of the belt-shaped member; a plurality of vertically extending positioning pins disposed between the first and second conveyors in such a manner as to be capable of being raised or lowered, so as to position the belt-shaped members as a front end of the belt-shaped member on the first conveyor and a rear end of the belt-shaped member on the second conveyor abut against each other when the positioning pins are raised so as to project upwardly from the first and second conveyors; upper joining pawls disposed above the positioning pins and capable of being raised or lowered; and lower joining pawls disposed below the upper joining pawls so as to join the front end of the belt-shaped member on the first conveyor and the rear end of the belt-shaped member on the second conveyor in cooperation with the upper joining pawls which have been lowered.
With such a conventional apparatus for joining the ends of belt-shaped members, a leading belt-shaped member must be transported from the first conveyor to the second conveyor prior to the starting of the joining operation. However, since the aforementioned lower joining pawls project slightly above the upper surfaces of the first and second conveyors, there have been cases where the leading belt-shaped member becomes caught by the lower joining pawls midway during transport, and therefore cannot be transported onto the second conveyor. In such a case, the operator is compelled to bring that belt-shaped member to the second conveyor, so that there has been a problem in that the operating efficiency is low, and automation cannot be implemented. In addition, when the belt-shaped members on the first and second conveyors abut against the positioning pins, the first and second conveyors run to transport the belt-shaped members placed thereon in the forward and reverse directions, respectively. At this time, the front and rear ends of these belt-shaped members move toward the positioning pins while coming into sliding contact with guide plates, respectively. Therefore, when the viscosity of the belt-shaped members changes due to a temperature change or the like, the frictional resistance of the belt-shaped members with respect to the guide plates also changes, thereby deteriorating the accuracy with which the front and rear ends of the belt-shaped members are fed. This causes the parallelism of the front and rear ends of the belt-shaped members to decline, causing faulty joining. Additionally, in cases where the longitudinal length of the belt-shaped members is short, a transporting and driving force imparted to the belt-shaped members from the first and second conveyors becomes small. If the viscosity of the belt-shaped members increases on such an occasion, the belt-shaped member may possibly adhere to the guide plate at a midway position. A wide gap is hence produced between the front and rear ends of the belt-shaped members, thereby resulting in faulty joining.